Directions

1. 1

   Rinse the Concord grapes and remove them from their stems. Sort through and discard any damaged grapes. You should have about 8 cups of grapes.

2. 2

   Working in batches, slip the skins off each grape by applying gentle pressure between your fingers. The meat and seeds will slip out as the skin releases. Set the skins aside in a bowl and place the grape pulp and seeds in a large heavy-bottomed pot.

3. 3

   Add the reserved grape skins to the pot with the pulp and seeds. Stir to combine.

4. 4

   Pour in the fresh lemon juice and add the granulated sugar. Stir well to combine all ingredients, making sure the sugar begins to dissolve into the grape mixture.

5. 5

   Place the pot over medium-high heat and bring the mixture to a rolling boil, stirring occasionally to help dissolve the sugar completely. Once boiling, reduce the heat to medium and maintain a steady, vigorous simmer.

6. 6

   Cook the mixture, stirring frequently to prevent sticking, for about 45 to 60 minutes. The jam will gradually darken and thicken. Watch for the consistency to reach the gel stage—when a spoonful drops from a wooden spoon and breaks into a sheet rather than separate drops.

7. 7

   Skim any white foam from the surface using a skimmer or large spoon. Add the butter and stir to incorporate—it helps reduce any remaining foam and adds a subtle smoothness.

8. 8

   Test the jam's readiness by placing a small spoonful on a chilled plate. Let it cool for a moment, then push your finger through it. If it wrinkles and the surface resists, the jam has set properly. If not, continue cooking for another 5 to 10 minutes and test again.

9. 9

   Once the jam reaches the desired consistency, remove from heat. Allow it to cool slightly, then ladle into sterilized jars, leaving about 1/4 inch headspace. Seal according to your preferred preservation method—either use a water-bath canning process for shelf-stable storage, or simply refrigerate in covered containers for up to three weeks.